The major long-range objectives of the proposed research are to elucidate the mechanisms operative in the modultion of RNA synthesis and RNA polymerase activities during various growth and developmental transitions, emphasizing studies on the regulation of RNA synthesis in rapidly proliferating tissues and DNA virus infected tissues. Our experimental approach has been to examine the levels and possible structural modification of the RNA polymerases and attempt to correlate these with nuclear transcription and in vivo RNA synthesis during the transition from a quiescent state to a rapidly proliferating state. To facilitate these studies, we have raised antibodies aginst RNA polymerases I, II, and III and have developed procedures for immunoprecipitating the RNA polymerases from cellular extracts and partially purified RNA polymerase preparations. We are using immunoprecipitation as a means to study the incorporation of 35S-methionine and 32P-orthophosphate into RNA polymerases from uninduced tissues. We are also studying conditions which promote faithful transcription in vitro.